The present invention relates to an ignition system of multispark type used mainly with an internal combustion engine.
Conventional ignition systems for producing a sufficient ignition energy at an ignition timing include a combination of an ignition system of capacitor discharge type and an ignition system of multispark type (as disclosed, for example, in U.S. Pat. No. 3906919), or include a system for supplying an ignition system of multispark type with the energy stored in an energy storage coil (as disclosed, for example, in U.S. Pat No. 4326493).
The former system, which is a simple combination of an ignition system of capacitor discharge type and an ignition system of multispark type, requires two types of coils, i.e., those for capacitor discharge and multiple ignitions as the primary windings of the ignition coil. This in turn requires three large-capacity switching devices for driving the primary windings, and a DC-DC converter exclusively used for the ignition system of capacitor discharge type. The resulting requirement of a great number of parts and a complicated construction poses the problem of high cost.
The latter conventional system, on the other hand, in which energy stored in the energy storage coil is only supplied to an ignition system of multispark type, has a disadvantage of small spark current in initial stage of ignition leading to an inferior ignitability as compared with the former conventional system, that is, the ignition system of capacitor discharge type.